Memory Device Interconnects and Method of Manufacture

ABSTRACT

An integrated circuit memory device, in one embodiment, includes a substrate having a plurality of bit lines. A first and second inter-level dielectric layer are successively disposed on the substrate. Each of a plurality of source lines extend through the first inter-level dielectric layer. Each of a plurality of source line vias extend through the second inter-level dielectric layer to each respective one of the plurality of source lines. Each of the plurality of staggered bit line contacts extend through the first and second inter-level dielectric layes to respective bit lines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 12/116,200filed May 6, 2008.

BACKGROUND OF THE INVENTION

There is a continuing need for improved flash memory devices. The needfor larger storage capacity devices, faster operating devices and/orlower power consuming devices continually drive further scaling ofmemory devices. However, the scaling of memory devices is constrained bydesign rules that are technology specific. The design rules specify theminimum feature sizes, spacings and overlaps for the component devicesand interconnects, and the maximum misalignment that can occur betweentwo masks. In addition, line width expansion and shrinkage throughoutfabrication also strongly affect the design rules.

Referring to FIG. 1, a representation of a memory cell array, accordingto the conventional art, is shown. The representation illustrates thegrid of word lines 110, bit lines 120, drain select gate, source selectgate, source line, and corresponding contacts. In the conventional art,the bit line interconnects may include polysilicon plugs (Poly 3),tungsten (W) clad layers, tungsten vias, and M1 interconnects. Thesource line interconnects may include polysilicon layer buried contacts(Poly 3), Titanium nitride (TiN) barrier layers, and tungsten (W)damascene M1 interconnects. The conventional interconnects require arelatively large number of masks. In addition, the bit lineinterconnects and source line interconnects are typically fabricatedseparately. Furthermore, the polysilicon portions of the conventionalinterconnects are characterized by a relatively high resistance.

In order to continue to scale memory devices, such as NAND flashmemories, there is a continuing need to further scale the interconnects.Preferably, the interconnects should be fabricated using as few masks aspossible. The resistance of interconnects should also preferably belower than conventional bit line and source line ground interconnects.

SUMMARY OF THE INVENTION

Embodiments of the present technology are directed toward integratedcircuit IC memory devices having staggered bit line contacts. The bitline contacts, bit line vias, the source lines and source line vias ofthe IC memory device are also substantially fabricated together. Inaddition, the bit line contacts, bit line vias, source lines and sourceline vias of the IC memory device are metal or a metal alloy.

In one embodiment, the integrated circuit memory device includes asubstrate having a plurality of bit lines. A first inter-leveldielectric layer is disposed on the substrate and a second inter-leveldielectric layer is disposed on the first inter-level dielectric layer.A plurality of source lines extend through the first inter-leveldielectric layer to the plurality of bit lines. Source line vias extendthrough the second inter-level dielectric layer to the source lines.Each of a plurality of staggered bit line contacts extend through thefirst inter-level dielectric layers to a respective one of the pluralityof bit lines. Each of a plurality of bit line vias extend through thesecond inter-level dielectric layer to a respective one of the pluralityof staggered bit line contacts. A metallization layer is coupled to oneor more of the plurality of source line vias and one or more of theplurality of staggered bit line vias.

In another embodiment, a method of fabricating the integrated circuitmemory device includes depositing a first inter-level dielectric layeron a substrate having a plurality of bit lines. A plurality of sourceline trenches are etched in the first inter-level dielectric layer and aplurality of staggered bit line contact openings are etched in the firstinter-level dielectric layer such that each opening extends to arespective one of the plurality of bit lines. A plurality of sourcelines are formed in the plurality of source line trenches and aplurality of staggered bit line contacts are formed in the plurality ofstaggered bit line contact openings from a first metal layer. A secondinter-level dielectric layer is then deposited on the first inter-leveldielectric layer. A plurality of source line via openings are etched inthe second inter-level dielectric layer such that each opening extendsto a source line. In addition, a plurality of staggered bit line viaopenings are etched in the second inter-level dielectric layer such thateach opening extends to a respective one of the plurality of staggeredbit line contacts. A plurality of source line vias are formed in theplurality of source line via openings and a plurality of staggered bitline vias are formed in the plurality of staggered bit line via openingsfrom a second metal layer.

In yet another embodiment, a method of fabricating an integrated circuitmemory device includes depositing a first inter-level dielectric layeron a substrate having a plurality of bit lines. A plurality of sourceline trenches are etched in the first inter-level dielectric layer. Inaddition, a plurality of staggered bit line contact openings are etchedin the first inter-level dielectric layer such that each opening extendsto a respective one of the plurality of bit line. A plurality of sourcelines are formed in the plurality of source line trenches and aplurality of staggered bit line contacts are formed in the plurality ofstaggered bit line contact openings from a first metal layer. A secondinter-level dielectric layer and an etch stop layer are then depositedon the first inter-level dielectric layer. A plurality of source linevia windows and a plurality of bit line via windows are etched in theetch stop layer proximate the source lines and the staggered bit linecontacts respectively. A plurality of trenches are etched in the firstmetallization oxide layer that each extend to a respective one of theplurality of source line via windows and the plurality of staggered bitline vias windows in the etch stop layer. The etching process iscontinued to each a plurality of the source line via openings throughthe second inter-level dielectric layer to a respective one of theplurality of the source lines, and a plurality of staggered bit line viaopenings through the second inter-level dielectric layer to a respectiveone of the first portion of the plurality of staggered bit linecontacts. A plurality of source vias are the formed in the plurality ofsource via openings, a plurality of staggered bit line vias are formedin the plurality of staggered bit line via openings and a firstmetallization layer is formed in the plurality of trenches in the firstmetallization oxide layer from a second metal layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of exampleand not by way of limitation, in the figures of the accompanyingdrawings and in which like reference numerals refer to similar elementsand in which:

FIG. 1 shows a representation of a memory cell array, according to theconventional art.

FIG. 2 shows a representation of a memory cell array, in accordance withone embodiment of the present technology.

FIGS. 3A-3D show a method of fabricating interconnects in an integratedcircuit (IC) memory device, according to one embodiment of the presenttechnology.

FIGS. 4A-4D shows various stages during fabrication of the IC memorydevice, in accordance with one embodiment of the present technology.

FIGS. 5A-5D show a method of fabricating interconnects in an integratedcircuit (IC) memory device, according to another embodiment of thepresent technology.

FIGS. 6A-6D shows various stages during fabrication of the IC memorydevice, in accordance with another embodiment of the present technology.

FIGS. 7A-7D show a method of fabricating interconnects in an integratedcircuit (IC) memory device, according to yet another embodiment of thepresent technology.

FIGS. 8A-8D shows various stages during fabrication of the IC memorydevice, in accordance with yet another embodiment of the presenttechnology.

FIGS. 9A-9B shows staggered bit line vias and contacts, in accordancewith embodiment of the present technology.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the embodiments of the presenttechnology, examples of which are illustrated in the accompanyingdrawings. While the present technology will be described in conjunctionwith these embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the scope of the invention asdefined by the appended claims. Furthermore, in the following detaileddescription of the present technology, numerous specific details are setforth in order to provide a thorough understanding of the presenttechnology. However, it is understood that the present technology may bepracticed without these specific details. In other instances, well-knownmethods, procedures, components, and circuits have not been described indetail as not to unnecessarily obscure aspects of the presenttechnology.

Integrated circuits such as memory devices may have hundreds, thousands,millions or more transistors, capacitors and the like, referred hereinto as semiconductor components, fabricated therein. The interconnectionsbetween semiconductor components are typically made in a plurality oflevels. As used here, the term “line” and “lines” refer to the portionsof interconnects that are arranged in planes that are substantiallyparallel to the wafer substrate. For example, a memory device typicallyincludes a plurality of source lines, bit lines, drain select gates,source select gates, and the like fabricated in one or more planes inthe interconnect layers. The terms “contact,” “contacts,” “via” and“vias” refer to the portions of interconnects that are substantiallyperpendicular to the wafer substrate used to connect lines in differentplanes or provide a connect at the surface of the die to lines orcomponents buried under one or more layers.

Embodiments of the present technology are directed to IC memory deviceswith staggered bit line contacts and bit line vias. The staggered bitline contacts and bit line vias may be formed at the same time as thesource lines and source line vias. In addition, the source line andsource line vias and/or the bit line contacts and bit line vias may beseparated into two portions vertically. Furthermore, the source line,source line vias, bit line contacts and bit line vias may be metal.

Referring now to FIG. 2, a representation of a memory cell array, inaccordance with one embodiment of the present technology, is shown. Theword lines 205, bit lines 210, drain select gates 215, source selectgates 220, source lines 225 and corresponding contacts/vias 230, 235,240 of the memory cell array are shown overlaid over a symbolicrepresentation of a NAND cell array. Each column of the NAND flashmemory array includes a drain select (e.g., MOSFET transistor) 245, aplurality of flash memory cells (e.g., floating gate MOSFET or SONOStransistors) 250, and a source select (e.g., MOSFET transistor) 255disposed along a corresponding bit line 210. A drain select gate 215 iscoupled to the gates of the drain selects 245 aligned in the first row.A respective one of a plurality of word lines 205 is coupled to thegates of each of the flash memory cells 250 along a given row. A sourceselect gate 220 is coupled to the gates of the source selects 255aligned in the last row.

The area of the semiconductor die consumed by the core memory cell unitis a function of the word line pitch (a) and the bit line pitch (b). Therest of the area of the semiconductor die is consumed by features thatare considered overhead with regard to the core memory cell unit. Theoverhead is a function of the select gate width (c), select gate wordline space (d), select gate-bit line contact space (e), via bottom on CDin y-direction (f), space between staggered contacts (g), selectgate-source line space (h), and source line width (bottom) (i). Theselect gate-bit line contact space (e), contact bottom CD in they-direction (f), the space between staggered contacts (g), selectgate-source line space (h) and source line width (i) are determined byprocess capability.

The bit line contacts/vias 230, 235 are staggered so that adjacent bitline contacts/vias are not in the same row. Staggering the bit linecontacts/vias 230, 235 increases the allowable misalignment tolerancewithout increasing the bit line pitch. The bit line contacts/vias 230,235, source lines 225 and source line vias 240 may be metal or metalalloy, such as tungsten, copper or the like. The metal source lines 225,source line vias 240 and bit line contacts/vias 230, 235 reduce theresistance of the source line interconnects and bit line interconnectsas compared to the conventional art. In addition, the bit linecontacts/vias 230, 235, source lines 225 and source line vias 240 may beformed at the same time. As a result, such NAND flash memories arecharacterized by improved bit line interconnects and source lineinterconnects.

Referring now to FIGS. 3A-3D, a method of fabricating interconnects inan integrated circuit (IC) memory device, according to one embodiment ofthe present technology, is shown. The method of fabricating mull levelinterconnects in an IC memory device will be further illustrated withreference to FIGS. 4A-4D, which shows various stages during fabricationof the IC memory device. The left side of FIGS. 4A-4D illustrate across-sectional view of FIG. 2 along view line A-A and the right side ofFIG. 4A-4D illustrate a cross-sectional view of FIG. 2 along view lineB-B. The method of fabricating the IC memory device begins, at 302, withvarious initial processes upon a wafer 402, such as cleaning,depositing, oxidation, doping, diffusion, implanting, photolithography,etching, chemical vapor deposition, evaporation, sputtering, epitaxy,annealing and/or the like. The initial fabrication processes form anarray of memory cells, and periphery circuits such as input/outputbuffers, data latch, address latch, address decoders and control logic.In one implementation, the IC memory device may be a NAND flash memorydevice.

At 304, a first inter-level dielectric layer (ILD0A) 404 is deposited onthe wafer 402. The inter-level dielectric may bechemical-vapor-deposited or sputtered silicon dioxide (SiO2), polyimideor the like. At 306, the inter-level dielectric layer 404 is thinnedand/or planarized. In one implementation, the deposited firstinter-level dielectric layer is thinned and planarized bychemical-mechanical polishing (CMP). At 308, a photo-resist is depositedand patterned by any well-known lithography process to form a sourceline mask. At 310, a plurality of trenches 410 are etched by anywell-known etching method. In one implementation, an etchant interactswith the portions of the first inter-level dielectric layer exposed bythe patterned resist until a plurality of source line trenches 410 areformed. At 312, the source line mask is removed utilizing an appropriateresist stripper or a resist ashing process.

At 314, a first metal layer is deposited on the first inter-leveldielectric 404. In one implementation, the metal may be titanium (Ti),titanium nitride (TiN), tungsten (W), or a multilayer metal such asTi/TiN/W. Referring now to FIG. 3B, excess metal of the first metallayer is removed to form source lines 416 in the source line trenches410, at 316. In one implementation, the first metal layer ischemical-mechanical polished (CMP) to form the source lines 416 in thesource line trenches 410.

Referring now to FIG. 4B, a second inter-level dielectric layer (ILD0B)418 is deposited, at 318. An anti-reflective coating (ARC) 420 may alsobe deposited, at 320. At 322, a photo-resist is deposited and patternedby any well-known lithography process to form a source line via mask. At324, a plurality of openings are etched by any well-known etching methodto form a plurality of source line via openings 424. In oneimplementation, an etchant removes the portions of the secondinter-level dielectric layer 418 exposed by the patterned resist layeruntil the plurality of openings extend to the source lines 416. At 326,the source line via mask is removed utilizing an appropriate resiststripper or a resist ashing process.

Referring now to FIG. 3C, a photo-resist is deposited and patterned byany well-known lithography process to form a staggered bit line contactmask, at 328. Referring now to FIG. 4C, a plurality of openings areetched by any well-known etching method to form a plurality of staggeredbit line contact openings 430, at 330. The bit line contact openings 430are staggered so that adjacent openings are not in the same row. In oneimplementation, an etchant removes the portions of the secondinter-level dielectric layer 418 and first inter-level dielectric layer404 exposed by the patterned resist layer until the plurality ofstaggered bit line contact openings 430 extend to respective bit lines431. At 332, the staggered bit line contact mask is removed utilizing anappropriate resist stripper or a resist ashing process.

Referring now to FIG. 4D, a second metal layer is deposited on thesecond inter-level dielectric 418 and in the openings 424, 430, at 334.In one implementation, the metal may be titanium (Ti), titanium nitride(TiN), tungsten (W), or a multilayer metal such as Ti/TiN/W. At 336,excess metal is removed to form a plurality of source line vias 436 anda plurality of staggered bit line contacts 437 in the second portion ofthe source line via openings 424 and the bit line contact openings 430respectively. In one implementation, the second metal layer ischemical-mechanical polished (CMP) to form the source line vias 436 inthe source line via openings 424 and the staggered bit line contacts 437in the staggered bit line contact openings 430. The resulting bit linecontacts 437 are staggered so that adjacent bit line contacts are not inthe same row.

At 338, an etch stop layer (ESL) is deposited. Referring now to FIG. 3D,a first metallization oxide layer 440 is deposited, at 340. At 342, aphoto-resist is deposited and patterned by any well-known lithographyprocess to form a first metallization layer mask. At 344, the exposedportions of the first metallization oxide layer 440 are etched by anywell-known isotropic etching method. At 346, a third metal layer isdeposited using an additive plating technique or the like to form firstmetallization layer to make connections 446, 447 to the source vias 436and the staggered bit line vias 437. In one implementation, the metalmay be copper (Cu), aluminum (Al), tungsten (W) or the like. At 348,fabrication continues with various other processes. The variousprocesses typically include cleaning, depositing, oxidation, doping,diffusion, implanting, photolithography, etching, chemical vapordeposition, evaporation, sputtering, epitaxy, annealing, passivation,cleaving and/or the like.

Referring now to FIGS. 5A-5D, a method of fabricating interconnects inan IC memory device, according to another embodiment of the presenttechnology, is shown. The method of fabricating multilevel interconnectsin the IC memory device will be further illustrated with reference toFIGS. 6A-6D, which shows various stages during fabrication of the ICmemory device. Again, the left side of FIGS. 6A-6D illustrate across-sectional view of FIG. 2 along view line A-A and the right side ofFIG. 6A-6D illustrate a cross-sectional view of FIG. 2 along view lineB-B. The method of fabricating the IC memory device begins, at 502, withvarious initial processes upon a wafer 602, such as cleaning,depositing, oxidation, doping, diffusion, implanting, photolithography,etching chemical vapor deposition, evaporation, sputtering, epitaxy,annealing and/or the like. The initial fabrication processes form anarray of memory cells, and periphery circuits such as input/outputbuffers, data latch, address latch, address decoders and control logic.In one implementation, the IC memory device may be a NAND flash memorydevice.

At 504, a first inter-level dielectric layer (ILD0A) 604 is deposited onthe wafer 602. The inter-level dielectric may bechemical-vapor-deposited or sputtered silicon dioxide (SiO2), polyimideor the like. At 506, the inter-level dielectric layer 604 is thinnedand/or planarized. In one implementation, the deposited firstinter-level dielectric layer is thinned and planarized bychemical-mechanical polishing (CMP). At 508, an anti-reflective coating(ARC) 608 may also be deposited. At 510, a photo-resist is deposited andpatterned by any well-known lithography process to form a source lineand staggered bit line contact mask. At 512, a plurality of openings areetched by any well-known etching method to form a plurality of sourceline trenches 612 and a plurality of staggered bit line contact openings613. In one implementation, an etchant interacts with the portions ofthe first inter-level dielectric layer 604 exposed by the patternedresist until a plurality of source line trenches 612 are formed thatextend to the bit lines 615. The etchant also removes the exposedportions of the first inter-level dielectric layer 604 until a pluralityof staggered bit line contact openings 613 are formed that extend to oneor more bit lines 615. The bit line contact openings 613 are staggeredso that adjacent openings are not in the same row. In addition, theaspect ratio of the staggered bit line contact openings result intapered walls. The staggering of the bit line contact openings enableuse of a larger tapering for the bit line contact openings. Referringnow to FIG. 5B, the source line and staggered bit line contact mask isremoved utilizing an appropriate resist stripper or a resist askingprocess, at 514.

Referring now to FIG. 6B, a first metal layer is deposited on the firstinter-level dielectric, at 516. In one implementation, the metal may betitanium (Ti), titanium nitride (TiN), tungsten (W), or a multilayermetal such as Ti/TiN/W. At 518, excess metal of the first metal layer isremoved to form a plurality of source lines 616 in the source linetrenches 612. Removal of the excess metal of the first metal layer alsoforms a plurality of bit line contacts 617 in the staggered bit linecontact openings 613. In one implementation, the first metal layer ischemical-mechanical polished (CMP) to form the source lines 616 and thestaggered bit line contacts 617. At 520, an etch stop layer (ESL) 620may be deposited.

Referring now to FIG. 6C, a second inter-level dielectric layer (ILD0B)622 is deposited, at 522. The inter-level dielectric may bechemical-vapor-deposited or sputtered silicon dioxide (SiO2), polyimideor the like. At 526, a second anti-reflective coating (ARC) 626 may alsobe deposited. Referring now to FIG. 5C, a photo-resist is deposited andpatterned by any well-known lithography process to form a source linevia and staggered bit line via mask, at 528. At 530, a plurality ofopenings are etched by any well-known etching method to form a pluralityof source line via openings 630 and a plurality of staggered bit linevia openings 631. In one implementation, an etchant removes the exposedportions of the second inter-level dielectric layer 622 exposed by thepatterned resist layer until a plurality of openings extend to thesource lines 616 and the staggered bit line contacts 617. Again, theaspect ratio of the staggered bit line via openings 631 result intapered walls. The staggering of the bit line via openings enable use ofa larger tapering for the bit line via openings.

At 532, the source line via and staggered bit line via mask is removedutilizing an appropriate resist stripper or a resist aching process.Referring now to FIG. 6D, a second metal layer is deposited on thesecond inter-level dielectric 622 and in the openings 630, 631, at 534.In one implementation, the metal may be titanium (Ti), titanium nitride(TiN), tungsten (W), or a multilayer metal such as Ti/TiN/W. At 536,excess metal is removed to form source line vias 636 and staggered bitline vias 637. In one implementation, the second metal layer ischemical-mechanical polished (CMP) to form the source line vias 636 inthe source line via openings 630 and the plurality of staggered bit linevias 637 in the staggered bit line via openings 631. The resulting bitline vias are staggered so that adjacent bit line vias are not in thesame row.

Referring now to FIG. 5D, a second etch stop layer (ESL) may bedeposited, at 538. At 540, a first metallization oxide layer 640 isdeposited. At 542, a photo-resist is deposited and patterned by anywell-known lithography process to form a first metallization layer mask.At 544, the exposed portions of the first metallization oxide layer 640are etched by any well-known etching method. At 546, a third metal layeris deposited using an additive technique such as plating or the like toform a first metallization layer to make connects to the source linevias 646 and the bit line vas 647. In one implementation, the metal maybe copper (Cu) aluminum (Al), tungsten (W) or the like. At 548,fabrication continues with various other processes. The variousprocesses typically include cleaning, depositing, oxidation, doping,diffusion, implanting, photolithography, etching, chemical vapordeposition, evaporation, sputtering, epitaxy, annealing, passivation,cleaving and/or the like.

It is appreciated that the staggering of the bit line vias and thetapering of the bit line vias increase the allowable alignment errors(e.g., relaxes lithography constraints) between the staggered bit linecontacts and staggered bit line vias respectively. For instance, asillustrated in FIGS. 9A and 9B, the combination of the tapering of thebit line vias and contacts and the staggering of the bit line vias andcontacts relaxes the lithography constraints such that the vias andcontacts maintain electrical contact with each other and do not overlapadjacent bit line vias and contacts even when there is a given amountmisalignment between the bit line vias and contacts 617, 631. Inaddition, the tapering of the bit line vias and contacts 617, 631 andthe source line and source line vias allow a more uniform metal fill.

Referring now to FIGS. 7A-7D, a method of fabricating interconnects inan IC memory device, according to another embodiment of the presenttechnology, is shown. The method of fabricating multilevel interconnectsin the IC memory device will be further illustrated with reference toFIGS. 8A-8D, which shows various stages during fabrication of the ICmemory device. Again, the left side of FIGS. 8A-8D illustrate across-sectional view of FIG. 2 along view line A-A and the right side ofFIG. 8A-8D illustrate a cross-sectional view of FIG. 2 along view lineB-B. The method of fabricating the IC memory device begins, at 702, withvarious initial processes upon a wafer 802, such as cleaning,depositing, oxidation, doping, diffusion, implanting, photolithography,etching, chemical vapor deposition, evaporation, sputtering, epitaxy,annealing and/or the like. The initial fabrication processes form anarray of memory cells, and periphery circuits such as input/outputbuffers, data latch, address latch, address decoders and control logic.In one implementation, the IC memory device may be a NAND flash memorydevice.

At 704, a first inter-level dielectric layer (ILD0A) 804 is deposited onthe wafer 602. The inter-level dielectric may bechemical-vapor-deposited or sputtered silicon dioxide (SiO2), polyimideor the like. At 706, the inter-level dielectric layer 804 is thinnedand/or planarized. In one implementation, the deposited firstinter-level dielectric layer is thinned and planarized bychemical-mechanical polishing (CMP). At 708, an anti-reflective coating(ARC) 808 may also be deposited. At 710, a photo-resist is deposited andpatterned by any well-known lithography process to form a source lineand staggered bit line contact mask. At 712, a plurality of openings areetched by any well-known etching method to form a plurality of sourceline trenches 812 and a plurality of staggered bit line contact openings813 in the first inter-level dielectric layer. In one implementation, anetchant interacts with the exposed portions of the first inter-leveldielectric layer 804 exposed by the patterned resist until a pluralityof source line trenches 812 are formed. The etchant also removes theportions of the first inter-level dielectric layer 804 until a pluralityof staggered bit line contact openings 813 are formed that extend toeach of one or more bit lines 815. The bit line contact openings 813 arestaggered so that adjacent openings are not in the same row. Inaddition, the aspect ratio of the staggered bit line contact openings813 and the etchant used result in tapered walls. The staggering of thebit line contacts openings enable use of a larger tapering for the bitline contact openings.

Referring now to FIG. 7B, the source line and staggered bit line contactmask is removed utilizing an appropriate resist stripper or a resistashing process, at 744. A first metal layer is deposited on the firstinter-level dielectric, at 716. In one implementation, the metal may betitanium (Ti), titanium nitride (TiN), tungsten (W), or a multilayermetal such as Ti/TiN/W. Referring now to FIG. 8B, excess metal of thefirst metal layer is removed to form source lines 818 in the pluralityof source line trenches 812, at 718. Removal of the excess metal of thefirst metal layer also forms staggered bit line contacts 819 in theplurality of staggered bit line contact openings 813. In oneimplementation, the first metal layer is chemical-mechanical polished(CMP) to form the source lines 818 and staggered bit line contacts 819.

Referring now to FIG. 8C, a first etch stop layer (ESL) 820 may bedeposited, at 720. In one implementation, the first ESL 820 may be anitride layer, or the like. At 728, a second inter-level dielectriclayer (ILD0B) 828 is deposited. The inter-level dielectric may bechemical-vapor-deposited or sputtered silicon dioxide (SiO2), polyimideor the like. At 730, a second ESL 830 is deposited. In oneimplementation, the second ESL 830 may be a nitride layer, or the liked.Referring now to FIG. 7C, a photo-resist is deposited and patterned byany well-known lithography process to form a source line via andstaggered bit line via mask, at 732. At 734, a plurality of openings areetched in the second ESL 830 by any well-known etching method to formsource line via windows and staggered bit line via windows in the secondESL 830. In one implementation, an etchant interacts with the exposedportions of second ESL 830 exposed by the patterned resist until aplurality of source line via and staggered bit line via windows areformed. At 736, the source line via and staggered bit line via mask isremoved utilizing an appropriate resist stripper or a resist ashingprocess.

At 738, a first metallization oxide layer 838 is deposited. A secondanti-reflective coating (ARC) 840 may also be deposited, at 740. At 742,a photo-resist is deposited and patterned by any well-known lithographyprocess to form a first metallization layer mask. Referring now to FIG.7D, the first metallization oxide layer 838 is etched by any well-knownetching method to pattern a first source line and staggered bit linemetal layer 844 in the first metallization oxide layer 838, at 744. Inaddition, the etchant interacts with the second inter-level dielectriclayer (ILD0B) 838 through the source line via windows and staggered bitline via windows in the second ESL 830 to form source line via openings845 and staggered bit line via openings 846 in the second inter-leveldielectric layer 822. In one implementation, an etchant interacts withthe portions of the first metallization oxide layer 838 to patterns thefirst metallization layer and then the second inter-level dielectriclayer 822 until the source line via openings 845 are formed that extendto the source line contacts 818. The etchant also removes the exposedportions of the second inter-level dielectric layer 822 until staggeredbit line via openings 846 are formed that extend to the staggered bitline contacts 819. Again, the aspect ratio of the staggered bit line viaopenings 846 and the etchant used result in tapered walls. Thestaggering of the bit line via openings enable use of a larger taperingfor the bit line via openings. At 746, the first metallization layermask is removed utilizing an appropriate resist stripper or a resistashing process.

At 748, a second metal layer 842 is deposited using an additivetechnique such as plating or the like. In one implementation, the metalmay be copper (Cu), aluminum (Al), tungsten (W) or the like. In anotherimplementation, the metal may be tungsten (W), titanium (Ti), titaniumnitride (TiN), or a multilayer metal such as Ti/TiN/W. The second metallayer forms source line vias 848, staggered bit line vias 849 and thesource line and bit line first metallization layer 850. The resultingbit line vias 819, 849 are staggered so that adjacent bit line vias arenot in the same row. At 750, fabrication continues with various otherprocesses. The various processes typically include cleaning, depositing,oxidation, doping, diffusion, ion implanting, photolithography, etching,chemical vapor deposition, evaporation, sputtering, epitaxy, annealing,passivation, cleaving and/or the like.

It is appreciated that the staggering of the bit line contacts and vias819, 849 and the source line and source line vias 818, 848, and thetapering of the portions of the bit line contacts and vias 819, 849 andsource line and source line vias 818, 848 increase the allowablealignment errors (e.g., relaxes lithography constraints) between the bitline vias and contacts 819, 849 and the source line and source line vias818, 848 respectively. For instance, as illustrated in FIGS. 9A and 9Bthe staggering of the bit line vias and contacts 819, 849 relax thelithography constraints in that the bit line vias and contacts 819, 849maintain electrical contact with each other and do not overlap adjacentbit line vias and contacts even when there is a given amount ofmisalignment between the bit line vias and contacts 819, 849. Inaddition, the tapering of the bit line vias and contacts 819, 849 andthe source line and source line vias 818, 848 allow a more uniform metalfill.

The foregoing descriptions of specific embodiments of the presenttechnology have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the present technology and its practicalapplication, to thereby enable others skilled in the art to best utilizethe present technology and various embodiments with variousmodifications as are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the Claimsappended hereto and their equivalents.

What is claimed is:
 1. An integrated circuit memory device comprising: asubstrate having a plurality of bit lines; a first inter-leveldielectric layer disposed on the substrate; a second inter-leveldielectric layer disposed on the first inter-level dielectric layer; aplurality of source lines that extend through the first inter-leveldielectric layer; a plurality of source line vias that extend throughthe second inter-level dielectric layer to each respective one of theplurality of source lines; a plurality of bit line contacts that extendthrough the first inter-level dielectric layer and second inter-leveldielectric layer to each respective one of the plurality of bit lines;and a metallization layer coupled to one or more of the plurality ofsource line vias and one or more of the plurality of bit line contacts.2. The integrated circuit memory device of claim 1, wherein theplurality of source lines are formed from a first metal layer.
 3. Theintegrated circuit memory device of claim 2, wherein the plurality ofbit line contacts and the plurality of source line vias are formed froma second metal layer.
 4. The integrated circuit memory device of claim1, wherein the plurality of bit line contacts and plurality of bit linevias are staggered so that adjacent ones of the bit line contacts andbit line vias are not in a same row.
 5. The integrated circuit memorydevice of claim 1, wherein the plurality of bit line contacts, theplurality of source lines and the plurality of source line vias areformed from a metal or metal alloy.
 6. The integrated circuit memorydevice of claim 1, wherein the plurality of bit line contacts, theplurality of source lines and the plurality of source line vias arecomprised of one or more metals selected from the group consisting oftungsten, titanium, and titanium nitride.
 7. The integrated circuitmemory device of claim 1, wherein each of the plurality of bit linecontacts are tapered.
 8. The integrated circuit memory device of claim1, wherein each of the plurality of source lines and each of theplurality of source line vias are tapered.
 9. A method of fabricating anintegrated circuit memory device comprising: depositing a firstinter-level dielectric layer on a substrate having a plurality of bitlines; etching a plurality of source line trenches in the firstinter-level dielectric layer; forming a plurality of source lines in theplurality of source line trenches from a first metal layer; depositing asecond inter-level dielectric layer on the first inter-level dielectriclayer; etching a plurality of source line via openings in the secondinter-level dielectric layer that each extend to a respective one of theplurality of source lines and a plurality of staggered bit line viaopenings in the second inter-level dielectric layer that each extend toa respective one of the plurality of staggered bit line contacts;etching a plurality of staggered bit line contact openings in the secondinter-level dielectric layer and the first inter-level dielectric layerthat each extend to a respective one of the plurality of bit lines; andforming a plurality of source line vias in the plurality of source linevia openings and a plurality of staggered bit line contacts in theplurality of staggered bit line contact openings from a second metallayer.
 10. The method according to claim 9, wherein forming theplurality of source lines comprises: depositing the first metal layerafter etching the source line trenches; and removing a portion of thefirst metal layer until the first metal layer only remains in the sourceline trenches.
 11. The method according to claim 9, wherein forming theplurality of source line vias and the plurality of staggered bit linecontacts comprises: depositing the second metal layer after etching thesource line via openings and the staggered bit line contact openings;and removing a portion of the second metal layer until the second metallayer only remains in the source line via openings and staggered bitline contact openings.
 12. The method according to claim 9, wherein: thesource line trenches are etched using a first mask; the source line viaopenings are etched using a second mask; and the staggered bit linecontact openings are etched using a third mask.
 13. The method accordingto claims 9, wherein each of the plurality of stagered bit line contactsare tapered.
 15. The method according to claim 9, wherein the firstmetal layer is tungsten, titanium, titanium nitrate or a multilayer oftitanium, titanium nitride and tungsten.
 16. The method according toclaim 9, wherein the second metal layer is tungsten, titanium, titaniumnitrate or a multilayer of titanium, titanium nitride and tungsten.